Field of the Invention
Embodiments of the invention relate to a display device and a method for controlling a luminance of the display device.
Discussion of the Related Art
Examples of a flat panel display include a liquid crystal display (LCD), a plasma display panel (PDP), an organic light emitting display, and an electrophoresis display (EPD). The liquid crystal display displays an image by controlling an electric field applied to liquid crystal molecules based on a data voltage. An active matrix liquid crystal display has advantages of a reduction in the production cost and an improvement of a performance with the development of the process technology and the driving technology. Thus, the active matrix liquid crystal display is the most widely used display device applied to almost all display devices including small mobile equipments and large-sized televisions.
Because the organic light emitting display is a self-emitting device, it has advantages of lower power consumption and thinner profile than the liquid crystal display requiring a backlight unit. Further, the organic light emitting display has advantages of a wide viewing angle and a fast response time. Thus, the organic light emitting display has expanded its market while competing with the liquid crystal display.
Each pixel of the organic light emitting display includes an organic light emitting diode (OLED) having a self-emitting structure. As shown in FIG. 1, the OLED includes organic compound layers, such as a hole injection layer HIL, a hole transport layer HTL, an emission layer EML, an electron transport layer ETL, and an electron injection layer EIL, which are stacked between an anode and a cathode. The organic light emitting display reproduces an input image using a phenomenon in which the OLED emits light when electrons and holes are combined in an organic layer of the OLED through a current flowing in a fluorescence or phosphorescence organic thin film.
The organic light emitting display may be variously classified depending on a light emitting material, a light emitting manner, a light emitting structure, a driving method, etc. The organic light emitting display may be classified into a fluorescence emission type and a phosphorescence emission type depending on the light emitting manner, and may be classified into a top emission type and a bottom top emission type depending on the light emitting structure. Further, the organic light emitting display may be classified into a passive matrix OLED (PMOLED) type and an active matrix OLED (AMOLED) type depending on the driving method.
It is necessary to reduce a luminance of a screen greatly affecting the power consumption so as to efficiently reduce the power consumption of the display device. The power consumption may be reduced through a simple method for reducing the luminance of the screen, but the image quality may be degraded.